Copolymers of bicyclic (meth)acrylates and alkyl (meth)acrylates and their use as rheology modifiers in fuels

ABSTRACT

The invention relates to a specific copolymer obtainable by co-polymerizing at least the following monomers: —at least one bicyclic (meth)acrylate ester—at least one C8-C24-alkyl (meth)acrylate—optionally, and preferably, at least one aromatic vinyl monomer; and —optionally other ethylenically unsaturated monomers, whereby the copolymer has a weight averaged molecular weight from 400,000 to 50,000,000 Dalton, as well as to the way to synthesize them and the use of such polymers to modify the rheology of a liquid in which they are soluble.

FIELD OF INVENTION

The present invention relates to a copolymer, its synthesis and uses ofthe copolymer.

BACKGROUND

Polymers have previously been used for modifying the rheology of a fluidcontaining the polymer. There is a need for polymers that can be used toadjust the flow and spray characteristics of a petroleum based fuel,such as gasoline and diesel fuel.

Liquid hydrocarbon fuels as such are typically not combustible. Theymust first be vaporized and mixed with air, or oxygen, to burn. Asmiddle distillate or heavier petroleum fuel fractions have low vaporpressures, efficient atomization is a critical aspect of spraycombustion of such fuels.

Atomization produces fine liquid fuel particles, whose large surfacearea leads to fast evaporation and thus rapid and efficient combustion.Even with efficient atomization stoichiometric combustion cannot beachieved. Limitation is imposed in this respect by the inability toreach a condition of perfect mixing in the time and size scale of thecombustion process and equipment. In order to get complete combustion,therefore, it is necessary to supply excess air to the system.

Excess air, to the extent it provides complete combustion, serves toincrease combustion efficiency. However, too much air can lead to adecrease in heat recovery. All of the oxygen not involved in thecombustion process as well as all of the nitrogen in the air is heatedand thus carries heat out of the stack. Further, the greater the excessair the greater the mass flow through the system and the shorter thetime scale for heat transfer. Hence, achieving efficient combustion andheat recovery requires a delicate balance of atomization and excess aircoupled with optimized combustion chamber and heat recovery systemdesigns.

GB 1 569 344 relates to the use of polymers, especiallypoly-isobutylene, to modify the fuel properties in an attempt to improvethe combustion efficiency. A problem with poly-isobutylene was foundthat it is very difficult to handle, which is exemplified by its Tg of−75° C. Other known polymers like poly-lauryl methacrylate also sufferfrom such a low Tg. Other polymers, such as poly isobornyl(meth)acrylates, were found to not give the desired rheologicalproperties and to be prohibitively expensive. Also most polymers withhigher Tg were found to suffer from insufficient solubility of thepolymer, making them unsuitable for changing the rheology of the liquid.Therefore, there still exists a need for alternative polymers with theability of modifying the rheology of liquids, such as petroleum basedfuel, at a reasonable cost.

SUMMARY OF INVENTION

One object of the invention is to provide a polymer with the ability tomodify the rheology of petroleum based fuel, in a manner that canpositively influence the combustion efficiency in an internal combustionengine run using such fuel.

The present inventors have found that this object can at least partly bemet by a polymer according to the present invention, which will now bemore described in detail.

The present invention relates to a copolymer obtainable bycopolymerizing the following monomers:

-   -   one or more bicyclic (meth)acrylate esters    -   one or more C8-C24-alkyl (meth)acrylates, whereof the C8-C24        alkyl group can be linear or branched, substituted or        unsubstituted, saturated or unsaturated,    -   optionally, and preferably, one or more aromatic vinyl monomers    -   optionally further ethylenically unsaturated monomers,        whereby the copolymer has a weight averaged molecular weight        (Mw) from 400,000 to 50,000,000 Dalton.

In the context of this invention, the term “(meth)acrylate” refers toacrylate and methacrylate.

It is noted that in prior art such as WO 2015/091513 and EP-A-0626442polymers with a similar composition have been proposed. However thepolymers produced therein have a molecular weight that is too low toallow for an efficient ability of modifying the rheology of liquids,such as petroleum based fuels. Other prior art, presenting highermolecular weight polymers, were found to suffer from solubility problemsin most solvents, largely due to their composition without bicyclic(meth)acrylate ester, resulting in unfavorable cloud points in manysolvents, particularly diesel fuels.

DETAILED DESCRIPTION OF THE INVENTION

The bicyclic (meth)acrylate ester contains a (meth)acryloyl radicalbonded to a six-membered carbon atom bridged ring and said group ofmonomers include products like decahydronaphtyl (meth)acrylates,2-norbornylmethyl methacrylate, and adamantyl (meth)acrylates, butpreferred are products according to formula (I)

wherein

R is H or —CH₃,

A is —CH₂—, —CH(CH₃)— or —C(CH₃)₂—, and

one or more M is covalently bonded to any carbon of the bicyclic rings,preferably to a carbon atom of the six-membered ring, and is selectedfrom the group consisting of hydrogen, halogen, methyl and methylaminogroup or a plurality thereof. Non-limiting examples of the bicyclic(meth)acrylate esters include isobornyl (meth)acrylate, bornyl(meth)acrylate, fenchyl (meth)acrylate, isofenchyl (meth)acrylate,norbornyl (meth)acrylate, cis, (endo) 3-methylamino-2-bornyl(meth)acrylate, 1,4,5,6,7,7-hexachlorobicyclo [2.2.1]-hept-5-ene-2-ol(meth)acrylate (HCBOMA) and 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]-hept-5-ene-2 methanol (meth)acrylate (HCBMA), and mixtures ofsuch bicyclic (meth)acrylates. In an embodiment the bicyclic(meth)acrylate ester is not 2-norbornylmethyl methacrylate. In andembodiment the bicyclic (meth)acrylate ester is not norbornyl(meth)acrylate The chlorinated compounds are less preferred since theycan liberate corrosive HCl when burned. A suitable bicyclic(meth)acrylate ester is isobornyl methacrylate. The bicyclic(meth)acrylate esters are known per se and may be prepared in knownfashion or may be obtained from commercial sources. The bicyclic(meth)acrylate is preferably chosen from monomers which, whenpolymerized, form a homopolymer that is soluble in the liquid,preferably in fuel, more preferably in the diesel fuel.

The C8-C24-alkyl (meth)acrylates of the invention are compounds whereina (meth)acryloyl radical is bonded to a fatty alkyl group, also known asfatty-alkyl (meth)acrylates, herein defined as a C8-C24 alkyl group,preferably a C10-C22 group, which can be linear or branched, substitutedor unsubstituted, saturated or unsaturated. Examples of the fatty alkyl(meth)acrylate include decyl (meth)acrylate, isodecyl (meth)acrylate,lauryl (meth)acrylate, methacrylic ester 13.0 (CAS#: 90551-76-1),tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, methacrylic ester17.4 (CAS#: 90551-84-1), and stearyl (meth)acrylate. Preferredfatty-alkyl (meth)acrylates are chosen from monomers which, whenpolymerized, form a homopolymer which is soluble in diesel fuel. Inanother embodiment isodecyl (meth)acrylate, lauryl (meth)acrylate,methacrylic ester 13.0 (CAS#: 90551-76-1), methacrylic ester 17.4 (CAS#:90551-84-1), and/or stearyl (meth)acrylate is used. In yet anotherembodiment, lauryl (meth)acrylate and/or methacrylic ester 13.0 (CAS#:90551-76-1) is used. Suitably lauryl methacrylate is used.

The aromatic vinyl monomer contains a vinyl group bonded to an aromaticgroup. Examples include styrene, substituted styrene, vinyl naphthalene,divinylbenzene, and mixtures thereof. Preferred substituted styrenesinclude ortho-, meta- and/or para-alkyl, alkyloxy or halogen substitutedstyrenes, such as methyl styrene, tert-butyloxy styrene, 2-chlorostyreneand 4-chlorostyrene. The preferred aromatic vinyl monomer is styrene.The aromatic vinyl monomer is preferably chosen from monomers which,when polymerized, form a homopolymer that is not soluble in the liquid,preferably in fuel, more preferably in the diesel fuel.

Further monomers that may participate in the copolymerization processare ethylenically unsaturated monomers different from the monomers (a),(b) and (c) defined above. Examples of such other monomers include loweralkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl(meth)(acrylate) and hexyl (meth) acrylate, but also 4-tert-butylstyrene, cationic, nonionic and anionic ethylenically unsaturatedmonomers, including, but not limited to, ethylenically unsaturatedacids, such as (meth)acrylic acid, maleic acid,2-acrylamido-2-methylpropane sulfonic acid, dimethylaminoethylmethacrylate, dimethylaminoethyl acrylate, N-[3-(dimethylamino) propyl]methacrylamide, N-[3-(dimethylamino) propyl] acrylamide,(3-acrylamidopropyl)-trimethyl-ammonium chloride, methacrylamido propyltrimethyl ammonium chloride, (meth)acrylamide, N-alkyl(meth)acrylamides, N-vinyl pyrrolidone, vinyl formamide, vinylacetamide, and N-vinyl caprolactams.

The copolymer may be synthesized by conventional methods for vinyladdition polymerization known to those skilled in the art, such as, butnot limited to, solution polymerization, precipitation polymerization,and dispersion polymerizations, including suspension polymerization andemulsion polymerization.

In an embodiment the polymer is formed by suspension polymerization,wherein monomers that are insoluble in water or poorly soluble in waterare suspended as droplets in water. The monomer droplet suspension ismaintained by mechanical agitation and the addition of stabilizers.Surface active polymers such as cellulose ethers, poly(vinylalcohol-co-vinyl acetate), poly(vinyl pyrrolidone) and alkali metalsalts of (meth)acrylic acid containing polymers and colloidal (waterinsoluble) inorganic powders such as tricalcium phosphate,hydroxyapatite, barium sulfate, kaolin, and magnesium silicates can beused as stabilizers. In addition, small amounts of surfactants such assodium dodecylbenzene sulfonate can be used together with thestabilizer(s). Polymerization is initiated using an oil solubleinitiator. Suitable initiators include peroxides such as benzoylperoxide, peroxy esters such as tert-butylperoxy-2-ethylhexanoate, andazo compounds such as 2,2′-azobis(2-methylbutyronitrile. At thecompletion of the polymerization, solid polymer product can be separatedfrom the reaction medium by filtration and washed with water, acid,base, or solvent to remove unreacted monomer or free stabilizer.

In another embodiment the polymer is formed by emulsion polymerization,one or more monomers are dispersed in an aqueous phase andpolymerization is initiated using a water soluble initiator. Themonomers are typically water insoluble or very poorly soluble in water,and a surfactant or soap is used to stabilize the monomer droplets inthe aqueous phase. Polymerization occurs in the swollen micelles andlatex particles. Other ingredients that might be present in an emulsionpolymerization include chain transfer agents such as mercaptans (e.g.dodecyl mercaptan) to control molecular weight and eloctrolytes tocontrol pH. Suitable initiators include alkali metal or ammonium saltsof persulfate such as ammonium persulfate, water-soluble azo compoundssuch as 2,2′-azobis(2-aminopropane)dihydrochloride, and redox systemssuch as Fe(II) and cumene hydroperoxide, and tert-butylhydroperoxide-Fe(II)-sodium ascorbate. Suitable surfactants includeanionic surfactants such as fatty acid soaps (e.g. sodium or potassiumstearate), sulfates and sulfonates (e.g. sodium dodecyl benzenesulfonate), sulfosuccinates (e.g. dioctyl sodium sulfosuccinate);non-ionic surfactants such as octylphenol ethoxylates and linear andbranched alcohol ethoxylates; cationic surfactants such as cetyltrimethyl ammonium chloride; and amphoteric surfactants. Anionicsurfactants and combinations of anionic surfactants and non-ionicsurfactants are most commonly used. Polymeric stabilizers such aspoly(vinyl alcohol-co-vinyl acetate) can also be used as surfactants.The solid polymer product free of the aqueous medium can be obtained bya number of processes including destabilization/coagulation of the finalemulsion followed by filtration, solvent precipitation of the polymerfrom latex, or spray drying of the latex.

One skilled in the art will recognize that certain surfactants andinitiator systems could leave residues in the polymer that will beundesirable in the fuel. These might include sulphur containing species,mono- and multivalent metal ions, and halide ions. One can either selectalternative surfactants and initiators that will not leave suchresidues, or choose an isolation/purification process that will removeor minimize any unwanted residues.

For the copolymers of the invention the amount of bicyclic(meth)acrylate ester (a) that is used in the monomer composition isgreater than 1, 5, 10, or 15 wt %, but suitably 20, 21, 23, 25, or 30 wt% or more, based on the weight of all monomers, because such copolymerswere found to have the desired solubility, as determined by the cloudpoint, in fuels.

In an embodiment, the copolymer is polymerized from:

20 to 95 wt % of the bicyclic (meth)acrylate ester (a);

5 to 80 wt % of the fatty-alkyl (meth)acrylate (b);

0 to 65 wt % of the aromatic vinyl monomer (c); and

0 to 50 wt % of further ethylenically unsaturated monomers (d), notbeing a monomer (a) or (b).

Throughout this document, the weight percentages of the monomer thatconstitute the copolymer, are based on the total weight of the monomersused, whereby the total weight of the monomers adds up to 100 wt %.

In an embodiment, the copolymer is polymerized from:

20 to 95 wt % of the bicyclic (meth)acrylate ester (a);

5 to 40 wt % of the fatty-alkyl (meth)acrylate (b);

0 to 65 wt % of the aromatic vinyl monomer (c); and

0 to 50 wt % of further ethylenically unsaturated monomers (d), notbeing a monomer (a) or (b).

In an embodiment, the copolymer of the invention is polymerized from

40 to 90 wt % of the bicyclic (meth)acrylate ester (a);

10 to 35 wt % of the fatty-alkyl (meth)acrylate (b);

5 to 50 wt % of the aromatic vinyl monomer (c); and

0 to 40 wt % of the further ethylenically unsaturated monomers (d), notbeing a monomer (a) (b) or (c).

In another embodiment the copolymer of the invention is polymerized from

60 to 85 wt % of the bicyclic (meth)acrylate ester (a);

15 to 25 wt % of the fatty-alkyl (meth)acrylate (b);

10 to 35 wt % of the aromatic vinyl monomer (c); and

0 to 30 wt. % of the further ethylenically unsaturated monomers (d) notbeing a monomer (a) (b) or (c).

For each of the embodiments it is preferred that the sum of monomer (a)and monomer (b) is greater than or equal to 35 wt. % more preferably,greater than or equal to 50%; and most preferably, greater than or equalto 55 wt. % of the total monomer composition.

For each of the embodiments it is preferred that the sum of monomer (a)and (c) is greater than or equal to 35 wt. %; more preferably, greaterthan or equal to 55%; and most preferably, greater than or equal to 65wt. % of the total monomer composition.

Preferably, in each embodiment, the amount of the other ethylenicallyunsaturated monomers (d) does not exceed 20 wt %, 15 wt %, 9 wt %, or 5wt %, and in certain embodiments, monomers a), b) and c) togetherconstitute 100 wt % of the monomers used to form the copolymer.

In a proviso, the copolymers of the invention may not be composed of atleast one bicyclic (meth)acrylate ester, at least one fatty-alkyl(meth)acrylate, and at least one lower-alkyl (meth)acrylate. In anotherproviso, the copolymers of the invention may not be composed of 60-70%w/w of bicyclic (meth)acrylate ester, 0.1-10% w/w fatty-alkyl(meth)acrylate, and 25-35% w/w lower-alkyl (meth)acrylate. Also they maynot be copolymers of at least one bicyclic (meth)acrylate ester, atleast one fatty-alkyl (meth)acrylate, at least one lower-alkyl(meth)acrylate, and at least one aromatic vinyl monomer, particularlynot copolymers wherein the weight percentage of bicyclic (meth)acrylateis, more than 15 weight percentage higher than the amount of aromaticvinyl monomer.

It was noted that a homopolymer of styrene is not soluble in B7 dieselfuel, but that a surprisingly large amounts of this monomer can becopolymerized with isobornyl methacrylate and fatty-alkyl (meth)acrylateto give highly soluble copolymers. For example, based on the weightfraction of each comonomer in the examples and using a linear mixingmodel, one would expect the cloud points which are significantly higherthan the ones actually found and reported herein. In a preferredembodiment the copolymer has a cloud point which is at least 5, morepreferably at least 10° C. below the value calculated using the linearmixing model.

If so desired, particularly to control the molecular weight and themolecular weight distribution of the polymer and/or to controlrheological behavior of solutions of the polymer, small amounts ofdivinylbenzene can be used in the mix of monomers. Typicallydivinylbenzene levels are below 5%, preferably below 2%, more preferablybelow 1%.

In the copolymer of the invention, the monomers may be arranged in anyfashion, such as in blocks or randomly. Preferably, the copolymer is arandomly arranged copolymer.

The weight averaged molecular weight (Mw) of the copolymer of theinvention, when measured in accordance with GPC-MALS method a) of theexperimental section, is preferably at least 400,000 Dalton (D), in anembodiment at least 500,000, 600,000, 700,000, 800,000, 900,000, and/orat least 1,000,000 D. In another embodiment the Mw of the copolymer ofthe invention is at least 1,500,000, suitably 2,000,000 D or more. Theupper molecular weight is determined by the solubility in the fluid inwhich it is intended to be used. Suitable the Mw is 50,000,000 or less,preferably less than 25,000,000. In an embodiment the Mw is 20,000,000,15,000,000, 10,000,000, 7,500,000, 6,000,000, and/or 5,000,000 or lessD. Polymers with a composition of the invention and a molecular weightof 1,000,000 to 50,000,000, preferably 2,000,000 to 25,000,000 D werefound to be useful at low concentrations, which made them particularlysuitable for the application in fuel, particularly for use in additivepackages for fuel. The polydispersity index (PDI), i.e. Mw/Mn, of thecopolymer of the invention was found not to be critical and is suitablyfrom 1, or 2, or 3, up to 10, or 8, or 6. In an embodiment the PDI isfrom 1 to 5 or from 1.5 to 4.

The glass transition temperature of the copolymer of the invention ispreferably from 50 to 190° C., more preferably from 65 to 150° C., andin another embodiment from 95 to 130° C., as determined by DifferentialScanning calorimetry (DSC). In this document the glass transitiontemperatures (Tg) were measured using a DSC Q200 (TA Instruments, NewCastle, Del.) with the following program:

-   1) Start DSC run with isothermal of 15 min at 20 degree C.;-   2) Ramp the temperature at 10 degree C./min to roughly 20 degree C.    above the Tg of the material;-   3) Run isothermal at that temperature for 5 min;-   4) Ramp temperature down from 20 degree C. above Tg at 20 degree    C./min to 20 degree C.;-   5) Run isothermal at 20 degree C. for 5 min;-   6) Start the Modulate mode with the process condition of +/−1.280    degree C. for every 60 second;-   7) Ramp the temperature at 2 degree C./min to 180 degree C.;

The composition of the polymer can be reliably estimated from therelative amounts of the monomers fed into the polymerization.Alternatively, the composition of the copolymer is suitably determinedfrom carbon-13 NMR spectra using a Varian MR-400 MHz and/or an AgilentDD2 MR 500 MHz NMR spectrometer.

The polymer of the invention is advantageously added to a petroleumbased fuel suitable for running combustion engines, such as fuelsconventionally known as gasoline and diesel fuels. The polymer ispreferably added to the fuel in an amount effective to obtain acombustion efficiency improving effect. Typically, the polymer of theinvention is added to the fuel to concentrations below 5000 ppm (partsper million), such as from 5, from 10, from 50, from 100 or from 500ppm, preferably up to 3000 or 1000 ppm. The term “ppm” equates to one mgper kg. In an embodiment, the copolymer is preferably present in a fuelcomposition in amount in the range of from 10 ppm to 300 ppm, morepreferably in the range of from 10 to 100, for example 25 ppm to 80 ppm,based on the total weight of the fuel composition.

The advantages of the copolymers of this invention are that (1) they arebetter suited to adjust the flow and spray characteristics of apetroleum based fuel than conventional polymers; (2) the Tg of thecopolymers is high enough to allow handling of the polymer as solids,(3) the cost of these copolymers will be lower than that ofpoly(isobornyl methacrylate) and other conventional polymers, and (4)they can be used in additive packages for use in fuel.

It is noted that the copolymers of the invention may also be added tofluids in general, non-polar, i.e. without a dipole, fluids orcompositions comprising non-polar fluids in particular, to modify therheology of such fluids. Suitably the viscosity of the fluids isincreased by dissolution of less than 1% w/w, preferably less than 0.5%w/w, of the copolymer, based on the weight of the total composition.

As used herein, “gasoline” refers to a liquid hydrocarbon based fuelsuitable for running a spark ignition engine, as is commonly known inthe art, and includes such fuels from petroleum raw material, renewableraw material, and mixtures thereof.

As used herein “diesel” refers to a liquid hydrocarbon based fuelsuitable for running a compression ignition engine, as is commonly knownin the art, and includes such fuels from petroleum raw material,renewable raw material, and mixtures thereof.

The term “consisting” wherever used herein also embraces “consistingsubstantially”, but may optionally be limited to its strict meaning of“consisting entirely”.

In the context of the invention the term ‘(meth)acrylate’ indicatesacrylate or methacrylate, and ‘(co)polymer’ indicates polymer orcopolymer. The term ‘polymer’ and the term ‘copolymer’ are used hereininterchangeably.

In additions to the hydrocarbons and the polymer, gasoline and dieselfuels may contain other additives as commonly used in the art. Fordetermining solubility in diesel, a diesel fuel B7 in accordance withthe EN 590 diesel fuel specification is used. An additive package is acombination of two or more components which can be added to a fuel.Because the amount of additive for each component is below 100%, theaccuracy of dosing is improved. The use of the combination alsofacilitates the handling since one composition is to be handled ratherthan the individual components. The additive package is suitably adissolution of the components in a solvent, because the controlledpre-dissolution of the polymer allows easier mixing with/dissolution ina fuel.

The copolymer of the invention is preferably soluble in diesel. Apolymer is considered to be soluble in accordance with the inventionwhen at least a 2.0 wt % solution of the polymer in the diesel at 25° C.can be made, if necessary after heating. Preferably a 2.0 wt % solutionof the polymer in the diesel at 8° C. can be made. In another embodimenta 9.1 wt % solution of the polymer in the diesel at 25° C. can be made.Preferably the copolymer of any embodiment of the invention, whenanalyzed as described below in the experimental section, shows a cloudpoint below 25° C., more preferably a cloud point below 15° C., and evenmore preferably a cloud point below 5° C.

EXAMPLES

A series of exemplary inventive copolymers and comparative polymers weremade using different combinations of isobornyl methacrylate, laurylmethacrylate, methacrylic ester 013.0, and other monomers. Isobornylmethacrylate was obtained from Sigma-Aldrich or Evonik (VISIOMER® terraIBOMA). Methacrylic ester 13.0 was obtained from Evonik (VISIOMER® terraC13-MA). Styrene and both lauryl and isobutyl methacrylate were obtainedfrom Sigma-Aldrich.

Molecular Weight:

Two different methods were used to determine polymer molecular weight.

Method A

Molecular weight was determined by GPC-MALS, 40° C. Quantitation was asemi-batch mode by analysis using a guard column only. Samples wereprepared by dissolving about 10 mg in 10 mL of tetrahydrofuran (mobilephase). Samples were further diluted with tetrahydrofuran as needed.

Column: Phenogel Guard 10̂6A (50 mm×7.8 mm)

Flow Rate: 0.5 ml/min THF

Injection: 50 μl

Column temperature: 40 C

Detection: Wyatt® Dawn Heleos 18 angle MALS 633 nm and

-   -   Wyatt Optilab T-REX Refractive Index Detector

Quantitation Zimm or Debye 1^(st) order of 2^(nd) order, with 5 to 18angles

Method B:

Molecular weight was determined by GPC-MALS. Samples were prepared bydissolving about 10 mg in 10 mL of tetrahydrofuran (mobile phase).

Column 30 cm×4.6 mm 10.0 μm Phenogel 10̂5 A—nominal limit 1 Million

Mobile Phase Stabilized Tetrahydrufuran

Flow Rate 0.40 ml/min

Injection 100 μl

Column Temperature 40° C.

Detection RI and LS with Wyatt Heleos MALS

Polymerization Procedure Synthesis Example S1. Preparation of Copolymerby Emulsion Polymerization Process Materials:

Initial Charge: Deionized water 632.8 g Aerosol ® OT-75 PG (sodiumdioctyl sulfosuccinate,  11.1 g 75% in propylene glycol and water;available from Cytec) 1% NaOH As needed Co-solvent: Acetone 139.6 gMonomer mix: Isobornyl methacrylate 117.0 g Styrene 117.3 g MethacrylicEster 13.0 (VISIOMER ® terra C13-MA,  66.1 g available from Evonik)Oxidant solution t-Butyl hydroperoxide, 70% 0.0400 g  Deionized water 3.75 g Reductant solution Deionized water  7.50 g Sodium ascorbate0.0739 g  Iron (II) sulfate heptahydrate, 0.25% in deionized water  0.60g

Polymerization Procedure

A 2 L, 4-neck round bottom flask is equipped with an overhead mechanicalstirrer, a Y-tube equipped with a condenser and nitrogen purge line, athermometer, and a stopper. To the flask were charged deionized waterand surfactant. The pH was checked and found to be within the desiredrange of 4 to 5 so no pH adjustment was made. A sub-surface nitrogenpurge was then initiated through the stopper.

In a separate container, isobornyl methacrylate, styrene, andmethacrylic ester 13.0 were combined.

An oxidant solution was then prepared by dissolving 0.0400 g t-butylhydroperoxide (70%) in 3.75 g deionized water.

While maintaining nitrogen purge, the monomer mixture and the acetoneco-solvent were slowly added the reaction vessel. During the addition,the agitation rate was gradually increased to 350 rpm.

Several minutes after the monomer mixture and the acetone co-solventadditions were completed, the agitation rate was slowed to 225 rpm.Using a thermostatted water bath, the reaction temperature was broughtto about 33° C. When the reaction temperature was about 33° C., theoxidizer solution was added to the reaction mixture in a single shot.

In a separate container, a reductant solution was prepared by dissolving0.0739 g sodium ascorbate and 0.60 g of an 0.25 wt. % solution of iron(II) sulfate heptahydrate in deionized water in 7.50 g deionized water.

About 5 minutes after the oxidant solution was added to the reactionmixture, the reaction temperature was 35° C. At this point, the darkblue reductant solution was added via syringe to the reaction vessel inone shot while maintaining nitrogen purge.

Heating was continued using a water bath. An exothermic reaction wasnoted to occur, and the temperature of the reaction increased to amaximum of about 52° C. after 1 h. It was thereafter maintained at orabove 43° C. using the water bath. As the reaction progressed, a bluishtint was noted in the emulsion, and it became increasingly moretranslucent, and a slight increase in viscosity was noted. After a totalof 6 h reaction time, the reaction was cooled and poured throughcheesecloth into a container. Coagulum (caught on cheesecloth) was notedand grit was measured.

The yield of polymer latex was 959 g. Solids (measured gravimetrically):30.23%. Molecular weight by GPC-MALS (Method B): Mw=5,700.000.

Solid polymer was isolated by adding the undiluted emulsion polymer to alarge excess of methanol. The resulting precipitate was collected byvacuum filtration and washed extensively with methanol.

Synthesis Examples S2S-22

Additional copolymers were prepared following the basic procedure usedto prepare Synthesis Example 1. The compositions and properties of thesepolymers and those of Synthesis Examples 51 are summarized in the Table1 below.

TABLE 1 Inventive copolymers. Tg Mw Ex. P# IBXMA Styrn IBMA LMA C13-MA(° C.) (kD) S1 39.0 39.0 0.0 0.0 22.0 79.9 5,700^(a) S2 25.0 22.0 41.511.5 0.0 76.3 7,100^(b) S3 25.0 22.0 36.0 17.0 0.0 67.1 11,000^(b)  S4P47 25.0 40.0 18.0 17.0 0.0 72.2 6,200^(b) S5 P50 25.0 58.0 0.0 17.0 0.082.5 5,600^(b) S6 25.0 22.0 28.0 25.0 0.0 58.1 20,000^(b)  S7 P52 25.050.0 0.0 25.0 0.0 64.2 12,000^(b)  S8 25.0 35.0 10.0 30.0 0.0 53.517,000^(b)  S9 25.0 22.0 18.0 35.0 0.0 44.3 33,000^(b)  S10 25.0 40.00.0 35.0 0.0 42.8 28,000^(b)  S11 44.0 25.0 0.0 0.0 31.0 62.611,400^(a)  S12 47.0 14.0 0.0 0.0 39.0 72.1 23,200^(a)  S13 62.0 27.00.0 0.0 11.0 118.7  5,900^(a) S14 62.0 11.0 0.0 0.0 27.0 102.6 8,200^(a) S15 69.0 15.5 0.0 0.0 15.5 123.0  6,100^(a) S16 80.0 15.0 0.00.0 5.0 153.1  2,500^(a) S17 80.0 0.0 0.0 0.0 20.0 154.5  5,900^(a) S18P69 65.0 0.0 30.0 0.0 5.0 126**  5,300^(a) IBXMA = isobornylmethacrylate; Styrn = styrene; IBMA = isobutyl methacrylate; LMA =lauryl methacrylate (Sigma-Aldrich); C13-MA: Methacrylic ester 13.0; CAS# 90551-76-1 (Evonik). **Tg value estimated on basis of Fox equation^(a)Molecular weight measurements by Method A. ^(b)Molecular weightmeasured by Method B.

Comparative Example 1

Polystyrene with a reported Mw of 280,000 was obtained fromSigma-Aldrich.

Comparative Example 2

Poly(isobutyl methacrylate) with an inherent viscosity of was obtainedfrom Polysciences.

Comparative Examples CE3-CE6 and Less Preferred Samples E7-E10

These copolymer were prepared following the basic procedure used toprepare Synthesis Example 51.

The compositions and properties of these polymers and those ofComparative Examples 1 and 2 are summarized in the Table 2 below.

TABLE 2 Comparative and less preferred Examples. Tg Mn Mw Ex P# IBXMAStyrn IBMA LMA C13-MA (° C.) (kDa) (kDa) PDI CE1 0.0 100.0 0.0 0.0 100* CE2 0.0 0.0 100.0 0.0 53*  CE3 100.0 0.0 0.0 0.0 202   982^(a) 2,196^(a)2.24^(a) CE4 25.0 28.0 47.0 0.0 94.6 n.d. CE5 25.0 43.0 32.0 0.0 96.6n.d. CE6 25.0 58.0 17.0 0.0 104.2  n.d. E7 P67 10.0 20.0 0.0 0.0 70.0 4.9 n.d. E8 P66 20.0 0.0 0.0 0.0 80.0 −21   n.d. E9 25.0 37.6 29.4 8.082.6 n.d. E10 25.0 58.0 8.5 8.5 133.8  n.d. IBXMA = isobornylmethacrylate; IBMA = isobutyl methacrylate; Styrn = styrene; LMA =lauryl methacrylate (Sigma-Aldrich); C13-MA: Methacrylic ester 13.0; CAS# 90551-76-1 (Evonik). ^(a)Molecular weight was determined by GelPermeation Chromatography (GPC) using narrow range polystyrenecalibration standards. Column: (300 mm × 7.5 mm ID), PhenomenexPhenogel, Linear 5μ (2) mixed; Mobile phase: Tetrahydrofuran; Columnoven: 40° C. Detection: RI Detector. Calibration was performed withconventional PS standards and using a 3^(rd) order curve. *Tg valuesfrom open literature.

Evaluation of Polymer Solubility in Diesel Fuel. Solubility IndexMethod:

In a 20 mL vial with a cap, 0.2 g of polymer was added to 9.8 g B7diesel fuel. The resulting mixture was loosely capped and stirredvigorously for 1 h at ambient room temperature (about 25° C.). Themixture was then heated to about 90° C. with stirring for 1 h. Theresulting mixture or solution was allowed to cool to ambient roomtemperature and stand for 24 h. Polymer solubility was then determinedby visual examination; polymers that showed any haze, turbidity or othersigns of phase separation were judged to be insoluble. Themixture/solution was then placed in a refrigerator set at 8° C. for 24h. Polymer solubility was then determined by visual examination;polymers that showed any haze, turbidity or other signs of phaseseparation were judged to be insoluble.

The B7 diesel fuel as used in these examples was based on a diesel basefuel having the characteristics given in Table 3 below.

TABLE 3 Parameter Method Units Cetane Number DIN 51773 — 53.5 Density @15° C. DIN EN ISO 12185 kg m−3 836.9 Distillation DIN EN ISO 3405 IBP °C. 179.2 5% v/v ° C. 203.2 10% v/v ° C. 214.4 20% v/v ° C. 232.0 30% v/v° C. 247.1 40% v/v ° C. 261.9 50% v/v ° C. 276.2 60% v/v ° C. 290.3 70%v/v ° C. 305.0 80% v/v ° C. 319.7 90% v/v ° C. 335.9 95% v/v ° C. 349.1FBP ° C. 358.2 Residue & loss % vol 1.9 Flash Point DIN EN ISO 2719 ° C.69.0 Viscosity @ 40° C. DIN EN ISO 3104 mm2 s−1 2.8687 Sulphur- DIN ENISO 20884 mg/kg <10 CFPP DIN EN 116 ° C. −29 Cloud point DIN EN 23015 °C. −8 Fatty acid methyl ester DIN EN 14078 % vol 6.4

Cloud Point Determination Method.

To a 4-neck 250 mL round bottom flask equipped with an overheadmechanical stirrer, thermometer, condenser and septum/stopper wascharged 5.0 g of polymer to 50.0 g of B7 diesel fuel. The resultingmixture was heated to 70-80° C. with stirring until a homogeneoussolution was obtained. In the case of some comparative examples, e.g.for polystyrene, the polymer did not dissolve in B7 diesel fuel evenafter stirring at 140° C. for 3 h. A portion of the resulting solutionwas transferred to a 40 mL vial while warm. For polymers with a cloudpoint above about 25° C., the solution was allowed to cool to about 25°C. while it was manually stirred with a thermometer. The reported cloudpoint is the temperature at which the solution was visibly became turbidor cloudy. For polymers with a cloud point below about 25° C., thesolution was cooled to a temperature below the point at which thesolution became visibly turbid or cloudy using an ice/water bath or adry ice/acetone bath. The resulting turbid/cloudy mixture was allowed togradually warm up to 25° C., while it was manually stirred with athermometer. The reported cloud point is the temperature at which thesolution became clear. As a check, once the cloud point of a polymer wasdetermined, clear solutions were gradually cooled (using cooling baths,if necessary) while stirring with a thermometer and the cloud point wasconfirmed. The results are summarized in Table 4.

TABLE 4 Polymer solubility evaluation results. Cloud point Tg @ 9.1% inB7 Ex P# IBXMA Styrn IBMA LMA C13-MA (° C.) (° C.) CE1 0.0 100.0 0.0 0.00.0 100*  >140 CE2 0.0 0.0 100.0 0.0 0.0 53*  45 CE3 100.0 0.0 0.0 0.00.0 202   −2 CE4 25.0 28.0 47.0 0.0 0.0 94.6 43 CE5 25.0 43.0 32.0 0.00.0 96.6 >50 CE6 25.0 58.0 17.0 0.0 0.0 104.2  >50 E7 P67 - 50 ppm 10.020.0 0.0 70.0 0.0  4.9 <25 E8 P66 - 50 ppm 20.0 0.0 0.0 80.0 0.0 −21  <25 E9 25.0 37.6 29.4 8.0 0.0 82.6 33 E10 25.0 58.0 8.5 8.5 0.0 133.8 46 S1 39.0 39.0 0.0 0.0 22.0 79.9 1 S2 25.0 22.0 41.5 11.5 0.0 76.3 <25S3 25.0 22.0 36.0 17.0 0.0 67.1 <25 S4 P47 - 50 ppm 25.0 40.0 18.0 17.00.0 72.2 16 S5 P50 - 50 ppm 25.0 58.0 0.0 17.0 0.0 82.5 19 S6 25.0 22.028.0 25.0 0.0 58.1 <25 S7 P52 - 50 ppm 25.0 50.0 0.0 25.0 0.0 64.2 −3 S825.0 35.0 10.0 30.0 0.0 53.5 <25 S9 25.0 22.0 18.0 35.0 0.0 44.3 <25 S1025.0 40.0 0.0 35.0 0.0 42.8 −5 S11 44.0 25.0 0.0 0.0 31.0 62.6 −1 S1247.0 14.0 0.0 0.0 39.0 72.1 −5 S13 62.0 27.0 0.0 0.0 11.0 118.7  −3 S1462.0 11.0 0.0 0.0 27.0 102.6  −5 S15 69.0 15.5 0.0 0.0 15.5 122.7  −2S16 80.0 15.0 0.0 0.0 5.0 153.1  0 S17 80.0 0.0 0.0 0.0 20.0 154.5  −5S18 P69 - 50 ppm 65.0 0.0 30.0 0.0 5.0 126**  −3 IBXMA = isobornylmethacrylate; Styrn = styrene; IBMA = isobutyl methacrylate; LMA =lauryl methacrylate (Sigma-Aldrich); C13-MA: Methacrylic ester 13.0; CAS# 90551-76-1. *Tg value from open literature. **Tg value estimated onbasis of Fox equation.

The homopolymer of styrene is not soluble in B7 diesel fuel, butsurprisingly large amounts of this monomer can be copolymerized withisobornyl methacrylate and lauryl methacrylate to give highly solublecopolymers. For example, based on weight fraction of each comonomer inExample S5, one would expect the cloud point at 9.1 wt. % of thiscopolymer to be about 78° C. using a linear mixing model. Instead, it is19° C., which is significantly and usefully different from the predictedvalue. Similarly, the predicted cloud point of S4, which contains 40 wt.% of the insoluble comonomer styrene and 18 wt. % of another insolublemonomer, isobutyl methacrylate, is about 61° C., which is above therange of sufficient solubility, while the actual cloud point is 16° C.,which is usefully within the preferred range of sufficient solubility.Also, the measured Tgs of these polymers are above 65° C., which is inthe more preferred range of Tg.

In comparative examples CE4-CE6 no fatty-alkyl (meth)acrylate is presentand these polymers have undesired solubility in diesel (cloud pointsgreater than 25° C.). Examples E7-E10 are less preferred since they haveeither an undesired low Tg or an undesired high cloud point, which makeshandling them very difficult.

Comparative Examples 7-9

In CE7 example 12 of EP-A-0626442 was reworked. The resulting polymershad a Mw of about 95 kD. The molecular weight was too low to efficientlyinfluence the rheology of a fluid in which the polymer is dissolved.

In CE8 the preparation 4 of U.S. Pat. No. 4,188,219 and in CE9 example 3of EP 1260278 were reworked. However in the rework of these bothexamples, no polymeric material could be produced.

Use Experiment

The products of the invention with a P number in Table 3 were evaluatedfor their effect on diesel rheology and influence on ignition delay,burn period, and maximum pressure increase in a combustion researchunit. First a concentrate was made in diesel containing at least 2.5 wt.% of the copolymer, which was subsequently diluted to a fuel with aconcentration (in mg/kg) of the polymer as indicated behind the Pnumber. The resulting data showed that a product in accordance with theinvention, when used in a diesel fuel, improved the fuel efficiency ofthe direct injection diesel engine running on said fuel. While notwishing to be bound by this theory, it is believed that the improvedefficiency is because the modified rheology due to the use of thepolymer in the fuel, leads to an improved atomization of the fuel and amore complete combustion.

1. A copolymer that is soluble for at least 2 wt % in diesel at 25° C.,the copolymer comprising the following monomers: at least one bicyclic(meth)acrylate ester, at least one C8-C24-alkyl (meth)acrylate, whereinthe C8-C24-alkyl group is linear or branched, substituted orunsubstituted, saturated or unsaturated, optionally at least onearomatic vinyl monomer, and optionally other ethylenically unsaturatedmonomers. wherein the copolymer has a weight averaged molecular weightfrom 400,000 to 50,000,000 Daltons.
 2. The copolymer according to claim1, wherein the bicyclic (meth)acrylate ester is of formula (I)

wherein R is H or —CH₃, A is —CH₂—, —CH(CH₃)— or —C(CH₃)₂—, and M iscovalently bonded to a carbon atom of the six-membered ring and isselected from the group consisting of hydrogen, a methyl group andcombinations thereof.
 3. The copolymer according to claim 1, wherein thecopolymer is a random co-polymer.
 4. The copolymer according to claim 1,comprising: 20 to 95 wt % of bicyclic (meth)acrylate ester, 5 to 80 wt %of C8-C24-alkyl (meth)acrylate, 0 to 65 wt % of aromatic vinyl monomer,and 0 to 50 wt % of other ethylenically unsaturated monomers, up to atotal of 100 wt %, wherein the weight percentages of the monomer arebased on the total weight of all the monomers.
 5. The copolymeraccording to claim 4, comprising 40 to 90 wt % of bicyclic(meth)acrylate ester, 10 to 35 wt % of C8-C24-alkyl (meth)acrylate, 5 to50 wt % of aromatic vinyl monomer, and 0 to 40 wt % of otherethylenically unsaturated monomers, up to a total of 100 wt %, whereinthe weight percentages of the monomer are based on the total weight ofall the monomers.
 6. The copolymer according to claim 5, comprising 60to 85 wt % of bicyclic (meth)acrylate ester, 15 to 25 wt % ofC8-C24-alkyl (meth)acrylate, 10 to 35 wt % of aromatic vinyl monomer, 0to 40 wt % of other ethylenically unsaturated monomers, up to a total of100 wt %, wherein the weight percentages of the monomer are based on thetotal weight of all the monomers.
 7. The copolymer according to claim 1,comprising a total of bicyclic (meth)acrylate ester and C8-C24-alkyl(meth)acrylate in an amount of 35 wt % or more.
 8. The copolymeraccording to claim 1, comprising a total of bicyclic (meth)acrylateester and aromatic vinyl monomer in an amount of 35 wt % or more.
 9. Thecopolymer according to claim 1, wherein the at least one bicyclic(meth)acrylate ester comprises isobornyl methacrylate.
 10. The copolymeraccording to claim 1, wherein the at least one C8-C24-alkyl methacrylatecomprises lauryl (meth)acrylate, methacrylic ester 13.0, (iso)decyl(meth)acrylate and combinations thereof.
 11. The copolymer according toclaim 1, wherein the at least one aromatic vinyl monomer comprisesstyrene.
 12. The copolymer according to claim 1, wherein the copolymerhas a solubility of at least 2.0 weight percent in diesel B7 at 25° C.13. The copolymer according to claim 1, wherein the copolymer has acloud point of 25° C. or lower in diesel B7 fuel.
 14. The copolymeraccording to claim 1, wherein the copolymer has a weight averagemolecular weight of at least 500,000 D.
 15. The copolymer according toclaim 1, wherein the copolymer has a glass transition temperature from50° C. to 190° C.
 16. An additive package for fuels comprising thecopolymer of claim
 1. 17. A method for the preparation of a copolymer ofclaim 1 comprising the step of radically polymerizing the monomers. 18.A method for the preparation of the additive package for fuels of claim16, the method comprising: (i) making a solution comprising a copolymerthat is soluble for at least 2 wt % in diesel at 25° C., the copolymercomprising the following monomers: at least one bicyclic (meth)acrylateester, at least one C8-C24-alkyl (meth)acrylate, wherein theC8-C24-alkyl group is linear or branched, substituted or unsubstituted,saturated or unsaturated, optionally at least one aromatic vinylmonomer, and optionally other ethylenically unsaturated monomers.wherein the copolymer has a weight averaged molecular weight from400,000 to 50,000,000 Daltons and (ii) adding one or more fuel additivesto the solution.
 19. A method for modifying the rheology of a fluid, themethod comprising dissolving the copolymer of claim 1 into the fluid,wherein the fluid is not a fuel for combustion engines.
 20. Thecopolymer according to claim 1, comprising 5 to 40 wt % of C8-C24-alkyl(meth)acrylate.